The influenza virus is a contagious virus that primarily affects the respiratory system. It can cause symptoms such as fever, cough, sore throat, body aches, and fatigue. There are several strains of the virus, including influenza A, influenza B, and influenza C, with influenza A being the most common and often responsible for seasonal outbreaks. Transmission occurs through respiratory droplets when an infected person coughs or sneezes. The virus can also survive on surfaces, making it possible to contract it by touching contaminated objects. Vaccination is a key method for preventing infection and reducing the severity of symptoms.